1. Technical Field
The present invention relates to a relay device, a communication system, a communication method, and a computer program with which even when Internet Protocol (IP) addresses of communication devices such as server devices and IP telephone sets are duplicated in a Transmission Control Protocol/Internet Protocol (TCP/IP) network, a communication device having a high communication priority is connected to the network in preference to others, thereby enabling prevention of non-arrival of data packets to the communication devices.
2. Description of Related Art
In recent years, as a TCP/IP network becomes increasingly pervasive, efforts to reduce communication costs are made by directly connecting an IP telephone set having IP functions to a network. In communication environment using TCP/IP, an IP address (a series of numbers of four bytes) for identifying on a network communication device such as a workstation, a server device or an IP telephone set connected to the network needs to be assigned to each communication device (refer to, e.g., Patent Document 1).
FIG. 15 is a block diagram showing the configuration of a switching hub device as a conventional relay device. A switching hub device 100 as a conventional relay device includes a switching controller 110, a storage section 120 for storing an Address Resolution Protocol (ARP) table 120a, an ARP table controller 130 and communication ports 140-1, 140-2, . . . , 140-N. The switching controller 110 performs transmission and reception of a data packet; when receiving a data packet, the switching controller 110 refers to the ARP table 120a, selects a communication port to which a communication device as a receiving end of the data packet is connected, and transfers the data packet to the selected communication port. Note that the ARP table 120a is a table for associating an IP address with a MAC address. The IP address is identification information for identifying a communication device on a network, and the MAC address is identification information for physically identifying a communication device.
The ARP table controller 130 determines whether or not the transmission source IP address and the transmission source MAC address of a received data packet are registered in the ARP table 120a, and additions and changes of the IP address and the MAC address are made to the ARP table 120a as needed. The communication ports 140-1, 140-2, . . . , 140-N are sections for connection with communication devices to and from which data packets are transmitted and received.
A conventional switching hub device analyzes a data packet transmitted from each of communication devices 150-1, 150-2, . . . , 150-N that are connected to communication ports to specify the receiving end of the data packet, and transmits the data packet to the specified communication device, thus completing transmission and reception of the data packet between communication devices.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2001-036561